Piezoelectric/electrostrictive device and production method thereof

ABSTRACT

A piezoelectric/electrostrictive device includes: a driving portion which is driven by displacement of a piezo-electric/electrostrictive element, a movable portion which operates on the basis of a drive of the driving portion, and a fixed portion for supporting the above driving portion and movable portion. It has a driving portion including thin plates facing each other and a thin film piezoelectric/electrostrictive element formed on the surface of at least one of the thin plates, and the above fixed portion and the above movable portion are joined by the driving portion. In this piezoelectric/electrostrictive element, the movable portion can largely be displaced, and it is not easily affected by a harmful vibration in operation, and it is excellent in mechanical strength, handling efficiency, impact resistance, and moisture resistance.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of U.S.application Ser. No. 09/242,642, filed Dec. 28, 1998, now U.S. Pat.6,239,534, the entirety of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a piezoelectric/electrostrictive devicehaving a movable portion which operates on the basis of displacement ofa piezoelectric/electrostrictive element, or apiezoelectric/electrostrictive device which can detect displacement of amovable portion by a piezoelectric/electrostrictive element, andparticularly relates to a piezoelectric/electrostrictive device which isexcellent in strength, impact resistance, and moisture resistance andhas a high amplitude efficiency and can largely operate the movableportion.

Recently, in the fields of optical and magnetic recording,precisionmachining or the like, a displacement element which can adjustan optical path length or a position in sub-micron precision has beenrequired, and the development of a displacement element which usesdisplacement based on the inverse piezoelectric effect orelectrostrictive effect caused when voltage is applied to apiezoelectric/electrostrictive material (for example, a ferroelectricsubstance) has been progressed.

For example, as shown in FIG. 2, a piezoelectric actuator 21 isdisclosed in Japanese Patent Laid-Open No. 10-136665, in which a fixedportion 25, a movable portion 24, and a beam portion 26 for connectingthese portions are unitarily formed by providing a hole portion 28 in aplate-like substance made of a piezo electric/electrostrictive materialand further, an electrode layer 22 is provided to the beam portion 26.

In the actuator 21, when voltage is applied to the electrode layer 22,the beam portion 26 expands and contracts in the direction of connectingthe fixed portion 25 and the movable portion 24 by the inversepiezoelectric effect or electrostrictive effect, and therefore, it ispossible to displace the movable portion 24 by arc-like displacement orrotary displacement in the plane of the plate-like substance.

However, in the actuator 21, since displacement in the expanding andcontracting direction of a piezoelectric/electro-strictive material(that is, in the direction in the plane of the plate-like substance) istransmitted to the movable portion as it is, displacement of the movableportion 24 is rather small.

Furthermore, in the actuator 21, since all parts are constituted by apiezoelectric/electrostrictive material which is a brittle andrelatively heavy material, there has been a problem in that the actuator21 itself is heavy and it may easily be affected by a harmful vibrationin operation (for example, a residual vibration or a noise vibration inhigh speed operation). In addition, the material has low mechanicalstrength and is inferior in handling efficiency, impact resistance, andmoisture resistance.

In the actuator 21, in order to solve the above problems, it has beenproposed to fill the hole portion 28 with a filler having flexibility,but it is clear that the efficiency of displacement based on the inversepiezoelectric effect or electrostrictive effect is lowered in the caseof using fillers.

The present invention is made due to such problems of the prior art, andit is an object thereof to provide a displacement element in which amovable portion can largely be operated and is not affected by a harmfulvibration in operation, and, additionally, has excellent mechanicalstrength, handling efficiency, impact resistance, and moistureresistance. As a result, the sensor element can detect a vibration ofthe movable portion accurately.

SUMMARY OF THE INVENTION

In the present invention, there is provided apiezoelectric/electro-strictive device comprising:

a driving portion which is driven by displacement of apiezoelectric/electrostrictive element;

a movable portion which operates on the basis of a drive of the drivingportion; and

a fixed portion for supporting said driving portion and movable portion,

wherein the device has a driving portion including thin plates facingeach other and a thin film piezoelectric/electrostrictive element formedon a surface of at least one of the thin plates and said fixed portionand said movable portion are connected by the driving portion.

As a specific mode of a piezoelectric/electrostrictive device of thepresent invention, a device can be cited, in which a movable portion anda fixed portion are shaped like a rectangular parallelepiped and thinplates facing each other are spanned so that the sides of the abovemovable portion and the above fixed portion are continuous.

The piezoelectric/electrostrictive device of the present invention is adevice in which a driving portion is driven in the directionperpendicular to the direction of displacement of apiezoelectric/electrostrictive element and a movable portion operates inthe plane including the driving direction of the driving portion.Furthermore, it is also possible to use the driving portion fordetection of displacement of the movable portion.

Moreover, the piezoelectric/electrostrictive device of the presentinvention is preferably a device having at least two driving portions,and it is preferably a device in which the width of a thin plate is 5 ormore times the thickness of the thin plate.

As a piezoelectric/electrostrictive element constituting apiezoelectric/electrostrictive device of the present invention, it ispreferable to use a layered type piezoelectric/electrostrictive elementin which a lower electrode, a piezoelectric/electrostrictive film, andan upper electrode are laminated, or a piezoelectric/electrostrictiveelement which comprises a piezoelectric/electrostrictive film, and afirst electrode and a second electrode having a comb-like structure andhas a structure where the first electrode and the second electrode aremutually engaged with a gap of a constant width between the mutual combtooth portions.

In the piezoelectric/electrostrictive device of the present invention,preferably, the movable portion, thin plate, and fixed portion are madeof an integrally formed ceramic, and more preferably, the movableportion, thin plate, and fixed portion are made of completely stabilizedzirconia or partially stabilized zirconia, and particularly preferably,at least the movable portion, thin plate, and fixed portion areconstituted by green sheet layered bodies.

Furthermore, in the piezoelectric/electrostrictive device of the presentinvention, preferably, the piezoelectric/electrostrictive filmconstituting a piezoelectric/electrostrictive element is made of amaterial containing lead zirconate, lead titanite, and lead magnesiumniobate as main components, and more preferably, the film is made of amaterial containing sodium bismuth titanate.

In the present invention, there is further provided a manufacturingmethod of a piezoelectric/electrostrictive device which has a drivingportion including thin plates facing each other and a thin filmpiezoelectric/electrostrictive element formed on the surface of at leastone of the thin plates, and a fixed portion and a movable portion shapedlike a rectangular parallelepiped, wherein the thin plates facing eachother are spanned so that sides of the movable portion and the fixedportion may be continuous, in which said manufacturing method comprisesthe steps of: obtaining a unitary layered body by laminating at leastone green sheet to be the thin plates, at least one green sheet where atleast one hole portion having a rectangular-like shape is formed, andfurther at least one green sheet to be the thin plates; forming apiezo-electric/electrostrictive element on the surface of the greensheet to be a thin plate by a thick film method or a thin film method;and cutting the layered body in the laminating direction of the greensheets so that the above hole portion having a rectangular-like shapemay be open on the side of the layered body after sintering the layeredbody.

In the present invention, there is further provided a light shutter forcontrolling penetration and shielding of light by relatively displacingtwo shielding plates, comprising:

a piezoelectric/electrostrictive device which comprises:

a driving portion driven by displacement of apiezoelectric/electro-strictive element;

a movable portion operating on the basis of a drive of the drivingportion; and

a fixed portion for supporting said driving portion and movable portion,and in which the device has a driving portion including thin platesfacing each other and a thin film piezoelectric/electrostrictive elementformed on a surface of at least one the thin plates and said fixedportion and said movable portion are connected by the driving portion,

wherein at least one shielding plate is attached to the movable portionof the piezoelectric/electrostrictive device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective illustration showing one embodiment ofa piezoelectric/electrostrictive device of the present invention.

FIG. 2 is a schematic perspective illustration showing one embodiment ofa conventional piezoelectric actuator.

FIG. 3 is a schematic explanatory drawing showing an operating mode of apiezoelectric/electrostrictive device of the present invention.

FIG. 4 is a schematic perspective illustration showing anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIGS. 5 (a) to (d) show still other embodiments of apiezoelectric/electrostrictive device of the present invention, andFIGS. 5 (a) and (b) are schematic perspective illustrations thereof, andFIGS. 5 (c) and (d) are explanatory drawings showing arrangements of aslit.

FIG. 6 is a schematic perspective illustration showing still anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIG. 7 is a schematic explanatory drawing showing still anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIG. 8 is a schematic explanatory drawing showing still anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIG. 9 is a schematic explanatory drawing showing still anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIG. 10 is a schematic explanatory drawing showing still anotherembodiment of a piezoelectric/electrostrictive device of the presentinvention.

FIG. 11 is a schematic perspective illustration showing one embodimentof a piezoelectric element constituting apiezoelectric/electro-strictive device of the resent invention.

FIG. 12 is a schematic explanatory drawing showing the relation betweena piezoelectric element constituting a piezoelectric/electro-strictivedevice of the present invention and the operating direction.

FIG. 13 is a schematic perspective illustration showing anotherembodiment of a piezoelectric element constituting apiezoelectric/electro-strictive device of the present invention.

FIG. 14 is a schematic perspective illustration showing still anotherembodiment of a piezoelectric element constituting apiezoelectric/electro-strictive device of the present invention.

FIG. 15 is a schematic perspective illustration showing one embodimentof the arranging method of an electrode wire of apiezo-electric/electrostrictive device of the present invention.

FIGS. 16 (a) and (b) are schematic explanatory drawings showing anotherembodiment of the arranging method of an electrode wire of apiezoelectric/electrostrictive device of the present invention.

FIG. 17 (a) and (b) are schematic explanatory drawings showing examplesof green sheets used in the manufacturing of apiezoelectric/electrostrictive device of the present invention.

FIG. 18 is a side view showing an embodiment of a manufacturing methodof a piezoelectric/electrostrictive device of the present invention.

FIGS. 19 (a) to (d) are process drawings showing an embodiment of amanufacturing method of a piezoelectric/electrostrictive device of thepresent invention.

FIGS. 20 (a) and (b) are schematic explanatory drawings showing anembodiment of a light shutter of the present invention, and FIG. 20 (a)is an illustration and FIG. 20 (b) is a top view.

FIG. 21 (a), (b), and (c) are schematic explanatory drawings showinganother embodiment of a light shutter of the present invention, and FIG.21 (a) is an illustration, and FIG. 21 (b) is a top view, and FIG. 21(c) is an enlarged view of a shielding plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A piezoelectric/electrostrictive device of the present invention will bedescribed below by referring to the drawings. However, the presentinvention is not limited to the illustrated examples.

By the way, in the following description, there are some cases where“piezoelectric” means “piezoelectric and/or electrostrictive.”Furthermore, “length” means a distance in the direction of connecting amovable portion and a fixed portion (z-axis direction in the figures),“width” means a distance in the hole portion penetrating direction(y-axis direction in the figures), and “thickness” means a distance inthe laminating direction of a piezoelectric element and a thin plate(x-axis direction in the figures).

1. Embodiment of Device

“Piezoelectric/electrostrictive device (hereafter, referred to simply as“device”)” used in the present specification is a concept coveringelements which mutually convert electric energy and mechanical energy byusing a piezoelectric/electrostrictive material. Accordingly, it ispreferably used for active elements such as various kinds of actuatorsor oscillators, especially for displacement elements using displacementbased on the inverse piezoelectric effect or electrostrictive effect,and it can also be used as passive elements such as an accelerationsensor element or an impact sensor element.

FIG. 1 is a schematic perspective illustration showing an embodiment ofa device 1 of the present invention. The device I is constituted by therespective parts of: a driving portion 3 which is driven by displacementof a piezoelectric element 2; a movable portion 4 which operates on thebasis of a drive of the driving portion 3; and a fixed portion 5 whichsupports the driving portion 3 and the movable portion 4.

The driving portion 3 is constituted by thin plates 6, 7 facing eachother and a thin-film-like piezoelectric element 2 formed on the surfaceof the thin plate 6, and by the thin plates 6, 7, the movable portion 4and the fixed portion 5 are connected. Accordingly, in the device 1, ahole portion 8 is formed in the direction perpendicular to the facingsurfaces of the thin plates 6, 7 facing each other.

As shown in FIG. 3, in the device 1, since the piezoelectric element 2is formed on the surface of the thin plate 6, the driving portion isdriven in the direction (b in the figure) perpendicular to thedisplacing direction (a in the figure) of the piezoelectric element.That is, since minute displacement in the expanding and contractingdirection of the piezo-electric element is transmitted to the movableportion 4 after being amplified to a large drive by using a bending ofthe thin plate 6, it is possible to cause relatively large displacementof the movable portion 4 (c in the figure).

Furthermore, since the device 1 is not a plate-like substance and themovable portion 4 and the fixed portion 5 are shaped like a rectangularparallelepiped and the thin plates 6, 7 are spanned so that the sides ofthe movable portion 4 and the fixed portion 5 are continuous, it ispossible to selectively raise the rigidity in the y-axis direction ofthe device. That is, in the device 1, it is possible to selectivelygenerate only an arc-like operation of the movable portion 4 in theplane (that is, in the XZ plane) including the driving direction of thedriving portion 3, and it is possible to restrain an operation in the YZplane of the movable portion 4 (operation in the so-called flappingdirection).

It is sufficient to form a piezoelectric element on the surface of atleast one thin plate of the facing thin plates like the device 1, but itis also possible to form piezoelectric elements 32 on both facing thinplates 36 like a device 31 shown in FIG. 4.

In such a constitution, by driving either of piezoelectric elements 32formed on thin plates 36, 37, it is possible to operate a movableportion 34 in the XZ plane like an arc similarly to the device 1, andfurther, it is possible to obtain an operation of expanding andcontracting the movable portion 34 in the Z-axis direction bysynchronously driving both piezoelectric elements 32.

Furthermore, by separately controlling both the piezoelectric elements32 to make a difference between the displacement amounts, it is possibleto easily obtain an operation in which an arc-like operation in the XZplane and an operation of expanding and contracting in the Z-axisdirection are synthesized. That is, as shown in FIG. 12, in a device 61of the present invention, the movable portion operates like an arc (e inthe figure) in the plane including the driving direction d of apiezoelectric element constituting the driving portion, or it operatesto expand and contract (f in the figure), or it operates in thedirection in which these are synthesized.

Still further, it is also possible that one of both piezoelectricelements 32 is a driving element and the other is a vibration detectingelement. That is, by using the driving portion of a device for detectionof displacement of the movable portion, it is possible to make thatfunction as an acceleration sensor or an impact sensor, and thedetection of trouble in the driving element becomes possible, and inaddition to that, if the voltage applied to the driving element iscontrolled on the basis of a signal from the detecting element, a moreaccurate travel control is possible. Furthermore, it is also possible todetect the vibration of the part itself where apiezoelectric/electrostrictive device is arranged and to give anoperation with an opposite phase for canceling the vibration to themovable portion and to obtain an effect of restraining the relativevibration of the movable portion as a result.

Furthermore, it is unnecessary to form a piezoelectric element for eachthin plate, and it is also possible to form the piezoelectric element bydividing one piece into a plurality of pieces if necessary. For example,in case of being divided in the width direction as shown in FIG. 5 (a),the displacement can be controlled for each separate piezoelectricelement, and therefore, displacement in the YZ plane (so-called flappingcomponent) can be restrained, and on the other hand, in case of beingdivided in the length direction as shown in FIG. 5 (b), bending iseasily performed at the divided portion, and therefore, the travel ofthe movable portion becomes larger and in the meantime, the resolutionof the travel can be improved. Furthermore, in case of dividing apiezoelectric element, it is possible that one piezoelectric element isa driving element and the other is a detecting element, and a compactstructure, and more accurate detection and control can be attained.

As mentioned above, in case of dividing a piezoelectric element for eachthin plate, it is also preferable to provide a slit 49 between thedivided piezoelectric elements 42—42 as shown in FIGS. 5 (c) and (d). Insuch a constitution, the thin plate is easily bent at the slit portion,and therefore, each piezoelectric element 42 can easily displace, and asa result, there is an advantage that displacement of a piezoelectricelement 42 can efficiently be transmitted to the movable portion.

Furthermore, as shown in FIG. 6, a device 51 having two or more drivingportions 53 provided is also preferable. In this case, since the drivingamount of each driving portion 53 is synergistically transmitted, it ispossible to more largely operate the movable portion 54, when comparedwith the case where there is only one driving portion.

Moreover, in the case where there are two or more driving portions, itis not always necessary that the movable portion and the fixed portionexist at both ends of the device, and as shown in FIG. 7, it is alsopossible that the fixed portions 55 are arranged at both ends and themovable portion 54 is arranged between the fixed portions 55—55.

In such a constitution, since the device 51 can surely be fixed thoughthe travel of the movable portion is decreased, there are advantagesthat the improvement of mechanical strength and impact resistance can beattained and that the operation in the YZ plane (operation in theso-called flapping direction) can be restrained.

As mentioned above, in case of providing a plurality of drivingportions, it is preferable to make the gap portion 59 between therespective driving portions 53—53 shorter than the fixed portion 55 orthe movable portion 54 as shown in FIG. 8. The reason is that the travelbecomes larger.

Furthermore, it is also possible to make the lengths of the respectivedriving portions 53 shorter as they approach the movable portion 54 asshown in FIG. 9. Such a constitution is preferable in that the movableportion can largely be operated and that a delicate adjustment is alsopossible since a fine control of the driving amount is possible at apart where the driving portion 53 is short while ensuring the drivingamount at a part where the driving portion 53 is long.

Furthermore, a device in which a notch portion 60 is formed between therespective driving portions 53—53 as shown in FIG. 10 is alsopreferable, though there is also a balance with mechanical strength. Thereason is that a thin plate 56 may easily be bent at the notch portion60, so that the travel of the movable portion can be increased.

Moreover, the device of the present invention has an advantage thatcomponent materials can properly be selected according to the requiredcharacteristics of the respective members as for the members except fora piezoelectric/electrostrictive element since it is not alwaysnecessary for the total to be constituted by apiezoelectric/electrostrictive material, in addition to the aboveeffects. That is, by making the members except for apiezoelectric/electrostrictive element of a light weight material, tomake it difficult to be affected by a harmful vibration in operation ispossible, and it is also easy to improve mechanical strength, handlingefficiency, impact resistance, and moisture resistance in a similarmanner.

Furthermore, since it is unnecessary to use a filler, the efficiency ofdisplacement based on the inverse piezoelectric effect orelectrostrictive effect is not lowered.

2. Components of Device

Next, the respective elements constituting a device of the presentinvention will separately and specifically be described by using anexample of the device 1 shown in FIG. 1.

(1) Movable Portion and Fixed Portion

The movable portion 4 is a part which operates on the basis of a drivingamount of the driving portion 3, to which various members are attachedaccording to the service objectives of the device 1. For example, incase of using the device 1 as a displacement element, it is sufficientto attach a member which requires a positional adjustment such as ashielding plate of a light shutter or a magnetic head.

The fixed portion 5 is a part which supports the driving portion 3 andthe movable portion 4, and the total of the device 1 is fastened bysupportably fastening the fixed portion 5 to a certain substance.

Furthermore, in some cases, a member such as an electrode wire forcontrolling the piezoelectric element 2 is arranged.

Materials for the movable portion 4 and the fixed portion 5 are notespecially limited as long as they have rigidity, but it is preferableto use ceramic to which the green sheet laminating method to bedescribed later can be applied. Specifically, zirconia coveringstabilized zirconia and partially stabilized zirconia, alumina,magnesia, silicon nitride or the like can be cited, and zirconia,especially stabilized zirconia and partially stabilized zirconia arepreferable in that they have high mechanical strength and hightoughness.

(2) Driving Portion

The driving portion 3 is a part which is driven by displacement of thepiezoelectric element 2, and it is constituted by facing thin plates 6,7 and a thin film piezoelectric element 2 formed on the surface the thinplate 6.

(i) Thin Plate

The thin plates 6, 7 are thin plate members with flexibility, and havefunction to amplify expanding and contracting displacement of thepiezoelectric element 2 provided on the surface as bending displacementand to transmit the displacement to the movable portion 4.

Accordingly, it is sufficient that the thin plates 6, 7 have flexibilityand have mechanical strength of a degree which is not broken by thebending deformation, and they can properly be selected by consideringresponsibility and operability of the movable portion.

Usually, the thickness of the thin plates 6, 7 is preferably about 5 to100 μm, and the total thickness of the thin plates 6, 7 and thepiezoelectric element 2 is preferably 10 to 500 pm. Furthermore, thewidth of the thin plates 6, 7 is preferably 30 to 500 pm, and it ispreferably 5 or more times the thickness of the thin plates 6, 7, and itis more preferably 8 or more times, from the view point of restrainingdisplacement in the YZ plane, that is, a flapping component and ofeffectively generating displacement in the XZ plane.

As a material for forming the thin plates 6, 7, ceramic similar to thatfor the movable portion 4 and the fixed portion 5 can preferably beused, and zirconia, especially stabilized zirconia and partiallystabilized zirconia can most preferably be employed since they have alarge mechanical strength even if they are shaped like a thin plate, andhave high toughness and low reactivity with a piezoelectric film or anelectrode material.

In case of using stabilized zirconia or partially stabilized zirconia asa material of the thin plates 6, 7, it is preferable to contain anadditive such as alumina or titania from the view point of being capableof relieving the residual stress when sintering the piezoelectric film.

(ii) Piezoelectric Element

The piezoelectric element 2 is constituted by a piezoelectric film andan electrode for applying voltage to the piezoelectric film, and it ispossible to use a conventionally known piezoelectric element such as aunimorph-type or a bimorphtype. For example, as shown in FIG. 11, it ispossible to preferably use a layeredtype piezoelectric element 62 inwhich a lower electrode 62 c, a piezoelectric film 62 a, and an upperelectrode 62 b are laminated, or the like.

Furthermore, it is also possible to use such a piezoelectric element 72as shown in FIG. 13, which is constituted by a first electrode 72 b anda second electrode 72 c with a comb-type structure, and which has astructure where the first electrode 72 b and the second electrode 72 care mutually engaged with a gap portion 73 of a constant width betweenthe mutual comb tooth portions. In FIG. 13, the first electrode 72 b andthe second electrode 72 c are arranged above the thin plate 76 and thepiezoelectric film 72 a, but it is also possible to form the electrodesbetween the thin film 76 and the piezoelectric film 72 a.

Furthermore, a piezoelectric element 82 shown in FIG. 14 is alsoconstituted by a first electrode 82 b and a second electrode 82 c with acomb-type structure, and it has a structure in which the first electrode82 b and the second electrode 82 c are mutually engaged with a gapportion 83 of a constant width between the mutual comb tooth portions.

The piezoelectric element 82 is constituted so that the piezoelectricfilm 82 a may be embedded in the gap portion between the first electrode82 b and the second electrode 82 c, and a piezoelectric element likethis can also preferably be used for a device of the present invention.In case of using a piezoelectric element having a comb-shaped electrodelike the piezoelectric elements 72, 82, it is possible to enlargedisplacement of a piezoelectric element by decreasing a pitch D of thecomb teeth.

By the way, it is preferable to form the piezoelectric element 2 on theoutside of the device 1 like the device 1 shown in FIG. 1 from the viewpoint of increasing displacement of the driving portion, but it is alsopossible to form that on the inside (that is, in the hole portion) ofthe device 1, and it is also possible to form them both on the insideand outside of the device 1.

As a piezoelectric film, piezoelectric ceramic is preferably used, butit is also possible to use electrostrictive ceramic, ferroelectricceramic, or antiferroelectric ceramic. However, in case of being usedfor a magnetic head or the like, the linearity between the travel of themovable portion and the applying voltage or output voltage is important,and therefore, it is preferable to use a material with a small strainhysteresis, and it is preferable to use a material with a coerciveelectric field of 10 or less kV/mm.

As specific piezoelectric ceramics, it is possible to cite the ceramicswhich contain the following substances as an independent substance or amixture: lead zirconate, lead titanate, lead magnesium niobate, leadnickel niobate, lead zinc niobate, lead manganese niobate, lead antimonystannate, lead manganese tungstate, lead cobalt niobate, bariumtitanate, sodium bismuth titanate, potassium sodium niobate, strontiumbismuth tantalate or the like. Especially, it is preferable to use amaterial whose main component is lead zirconate, lead titanate, and leadmagnesium niobate, or a material whose main component is sodium bismuthtitanate, from the view point of being capable of obtaining a materialwhich has a high electromechanical coupling factor and piezoelectricconstant, and has a small reactivity with the thin plate (ceramic) whensintering the piezoelectric film, and has a stable composition.

Furthermore, it is also possible to use the ceramics which containoxides or the like of the following substances as an independentsubstance or a mixture in addition to the above piezoelectric ceramics:lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium,zinc, nickel, manganese, cerium, cadmium, chromium, cobalt, antimony,iron, yttrium, tantalum, lithium, bismuth, tin or the like. For example,in some case, it is possible to obtain advantages that the coerciveelectric field and piezoelectric characteristics or the like can beadjusted, by making zirconate, titanate, and magnesium niobate, whichare main components, contain lanthanum or strontium.

An electrode of the piezoelectric element is preferably made of a metalwhich is solid at room temperature and is excellent in conductivity, andfor example, a simple metal or an alloy of the following substances isused: aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc,niobium, molybdenum, ruthenium, palladium, rhodium, silver, tin,tantalum, tungsten, iridium, platinum, gold, wire or the like, andfurther, it is also possible to use a cermet material in which the samematerial as that of the piezoelectric film or thin plate is scattered inthese.

The selection of a material for an electrode in the piezo-electricelement is determined depending on the forming method of a piezoelectricfilm. For example, in case of forming a piezoelectric film by sinteringon a first electrode after forming the first electrode on a thin plate,it is necessary to use a metal with a high melting point such asplatinum which does not change at the sintering temperature of thepiezoelectric film, for the first electrode, but for the secondelectrode formed on a piezoelectric film after forming the piezoelectricfilm, a metal with a low melting point such as aluminum can be used,since the electrode can be formed at a low temperature.

Various modes of electrode wires from the piezoelectric element can beconsidered, and for example, as shown in FIG. 15, in a device 91 inwhich piezoelectric elements 92 are formed on both facing thin plates96, a mode can be cited, in which lower electrodes 92 c of twopiezoelectric elements 92 are common and are pulled out to the side ofone surface of the fixed portion 95 where a hole portion 98 is open, andupper electrodes 92 b are directly pulled out to the side of the surfaceof the fixed portion 95 where each piezoelectric element 92 is formed.

A mode like this is preferable in that the device can be fixed with highreliability and it can be made compact, since no electrode is formed ata part (99 in the figure) on the side of other surface of the fixedportion 95 where a hole portion 98 is open so that the device can befixed by using that part.

Furthermore, it is also possible to be a mode where both the upperelectrode 92 b and the lower electrode 92 c are pulled out to the sideof the surface of the fixed portion 95 where the respectivepiezoelectric elements 92 are formed so that the electrodes 92 b , 92 cmay be in parallel as shown in FIG. 16 (a), or a mode where both theupper electrode 92 b and the lower electrode 92 c are separately pulledout to the side of the surface of the movable portion 94 and the side ofthe surface of the fixed portion 95 where each piezoelectric element 92is formed.

3. Manufacturing Method of Device

Here, a manufacturing method of a device of the present invention willbe described.

In a device of the present invention, it is preferable that a materialfor the respective members is ceramics and the device is manufactured byusing the green sheet laminating method. The reason is that thereliability of the joint portions of the respective members can beimproved by using the green sheet laminating method capable ofintegrally forming a device, and in addition to that, it is possible tomass-produce devices with the above excellent characteristics bysimplifying the manufacturing process.

(1) Manufacturing of Layered Body

First, a binder, a solvent, a dispersant or the like is added to andmixed with a ceramic powder such as zirconia to prepare slurry, andafter the slurry is subjected to degassing treatment, a green sheethaving a specified thickness is produced by a method such as the reverseroll coater method or the doctor blade method.

Next, the green sheet is processed to have various shapes shown in FIGS.17 (a) and (b) by a method such as the punching method using a mold.

A green sheet 101 is a green sheet to be mainly a thin plate after thesintering, and a green sheet 102 where at least one hole portion havinga rectangular-like shape 103 is formed is a member to be a movableportion and a fixed portion. It is possible to obtain a plurality ofdevices at a time, or to obtain at least a device with a plurality ofmovable portions by forming one or more lines of hole portions 103 inparallel.

A thickness required for a thin plate, a movable portion, and a fixedportion can be obtained by laminating at least one green sheet 101 andat least one green sheet 102.

A layered body can be obtained in such a way where the green sheets arelaminated in the order of a green sheet 101, a green sheet 102, and agreen sheet 101 while performing the positioning by using a referencehole 104 and they are integrated by using a method such as thethermo-compression bonding (FIG. 19 (a)).

When there is a situation in which the green sheet 102 is thick and theforming of the hole portion 103 is difficult or the like, it is alsopossible to obtain a final layered body 108 by forming the upper andlower parts of the layered body 105 and then joining the upper and lowerparts to obtain the layered body 108 such that the hole portions 103face each other as shown in FIG. 18.

As for the layered body 108, it is necessary to form in advance aconnecting hole 106 between a part to be the hole portion 103 of thegreen sheet 102 and the outer space in the green sheet 102, or to borethe connecting hole 106 after obtaining the layered body.

However, the shape of the connecting hole 106 is not especially limitedas long as each hole portion 103 is connected to the outer space, and itis also possible to be a shape of separately connecting each holeportion 103 to the outer space as shown in FIG. 19 (d) besides a shapeof penetrating a plurality of hole portions 103 as shown in FIGS. 19 (a)and (b).

(2) Formation of Piezoelectric/Electrostrictive Element

In the manufacturing method of the present invention, it is possible toform a piezoelectric element 107 on the surface of a green sheet 101 tobe a thin plate by a thick film method such as the screen printing,dipping, painting, or electrophoresis method, or by a thin film methodsuch as the ion beam method, sputtering, vacuum evaporation, ionplating, chemical vapor deposition (CVD), or plating (FIG. 19 (b)).

By forming a piezoelectric element by a film forming method like this, apiezoelectric element and a thin plate can be integrally bonded andarranged without using adhesives, and the reliability and repeatabilityare ensured, which makes the integration easy.

However, in the manufacturing method of the present invention, it ispreferable to form a piezoelectric element 107 by thick film methods.The reason is that these methods make it possible to form apiezoelectric film by using paste and slurry, or suspension andemulsion, sol or the like whose main component is piezoelectric ceramicparticles having an average particle diameter of 0.01 to 5 μm,preferably of 0.05 to 3 μm and a preferable piezoelectric operatingcharacteristics can be obtained. Particularly, the electrophoresismethod has an advantage that a film can be formed at a high density andwith a high shape accuracy.

Specifically, after sintering a layered body under a predeterminedcondition, a lower electrode is printed and sintered at a predeterminedposition on the surface of the sintered green sheet 101, and next, apiezoelectric film is printed and sintered, and further, an upperelectrode is printed and sintered, so that a piezoelectric element canbe formed (FIG. 19 (b)). Furthermore, an electrode wire for connectingthe electrode to a driving circuit should be printed and sintered.

Here, when materials are selected so that the sintering temper-atures ofthe respective members may sequentially be lower by using platinum (Pt)as the lower electrode, lead zirconate titanate (PZT) as thepiezoelectric film, gold (Au) as the upper electrode, and silver (Ag) asthe electrode wire, the re-sintering of a material sintered before thatmoment does not occur in a certain sintering stage, and it is possibleto avoid the occurrence of trouble such as exfoliation or aggregation ofelectrode materials or the like.

By selecting a proper material, it is possible to sequentially print therespective members and electrode wires of a piezoelectric element 107and to integrally fire them at a time, and on the other hand, it is alsopossible to provide the respective electrodes or the like at a lowtemperature after forming a piezoelectric film.

Furthermore, it is also possible to form the respective members andelectrode wires of the piezoelectric element by a thin film method suchas sputtering or vapor evaporation, and in this case, the heat treatmentis not always necessary.

It is also preferable that a piezoelectric element 107 is formed inadvance at position finally to be a thin plate of a green sheet 101 andis sintered simultaneously with a layered body 108. As a method ofsintering a piezoelectric element 107 and a layered body 108 at the sametime, a method can be cited, where a piezoelectric film is formed bypress molding using a mold, tape molding using a slurry material or thelike and this piezoelectric film before sintering is laminated on agreen sheet 101 by thermo-compression bonding and they aresimultaneously sintered to produce a movable portion, a driving portion,a thin plate, and a piezoelectric film at the same time. However, whenthis method is used, it is necessary to form in advance an electrode ona thin plate or a piezoelectric film by using the above film formingmethod.

The sintering temperature of a piezoelectric film is properly determinedon the basis of a material forming this, and usually, it is 800° C.to1400° C., and preferably, it is 1000° C. to 1400° C. In this case, inorder to control a composition of a piezoelectric film, it is preferableto perform the sintering in the presence of an evaporation source of amaterial of a piezoelectric film. In case of sintering a piezoelectricfilm and a layered body 108 at the same time, it is necessary to unifythe sintering conditions of both.

In case of manufacturing a device in which piezoelectric elements areformed on both facing thin plates, piezoelectric films, electrodes orthe like should be printed on both surfaces of a layered body.

In such a case, it is necessary to take an action for preventing theprinted piezoelectric film, electrode or the like from adhering to theprinting stage by a method <1>of performing the printing on a printingstage where a concave portion is provided in the stage, or a method<2>of performing the printing of the other surface, after forming aframe-like convex portion around the printing part on at least oneprinting surface of the layered body and performing the printing of thesurface having the convex portion formed, or the like.

(3) Sintering and Cutting of Layered Body

In the above layered body, a plurality of devices can be obtained at thesame time in such a way where the formation of a notch portion and thetreatment of coating and shielding of a piezoelectric element and anelectrode wire are performed if necessary, and after that, the sinteringis performed at a temperature of 1200° C. to 1600° C., and the cuttingis performed in the laminating direction of the green sheet so that thehole portion having a rectangular-like shape 103 may be open on the sideof the layered body (FIG. 19 (c)). As a cutting method, it is possibleto apply a laser beam machining using a YAG laser beam, an eximer laserbeam or the like, and an electron beam machining in addition to a dicingmachining, a wire saw machining or the like (mechanical machining).

In the manufacturing method of the present invention, the cutting isperformed so that the hole portion having a rectangular-like shape 103may be open on the side of the layered body 103.

Such a cutting has an advantage that not only a plurality of devices canbe separated but also thin plates and a hole portion of a device (thinplates 6, 7 and a hole portion 8 in the device 1 in FIG. 1) can beformed at a time, and it is preferable in that it is possible to easilyobtain a complex structure in which two or more rectangularparallelepipeds are connected by thin plates and which cannot easily bemanufactured.

Furthermore, by properly changing the number of formations and theposition of formation of the hole portions 103 in the green sheet 102,or the cutting position of the layered body 108, it is also possible toeasily form a device having a plurality of driving portions (FIGS. 6 to8) and a device having different lengths of driving portions (FIG. 9).

A device of the present invention can also be produced by press moldingusing a molding die, slip casting, injection molding or the like inaddition to the above producing method using a green sheet. Furthermore,a producing method of joining the respective component members preparedas different bodies is also possible, but it has a problem from the viewpoint of reliability since damages or the like easily occur in thejunctions, in addition to low productivity.

4. Examples of Application of Device

Finally, as one example of the applications of a device of the presentinvention, an example in which a device of the present invention isapplied to displacement element for a light shutter will be described.“Light shutter” expressed in the present specification means afunctional element which controls penetration and shielding of light byrelatively displacing two shielding plates, and since it can performON/OFF control of light and light volume control, it can function as alight switch or a light aperture.

A light shutter of the present invention is a shutter in which at leastone shielding plate of two shielding plates is attached to a movableportion of a device of the present invention.

For example, a light shutter 110 shown in FIGS. 20 (a), (b) is made oftwo units 111 A, 111 B equipped with devices of the present inventionand shielding plates, and two shielding plates 113A, 113B arerespectively attached to movable portions 114A, 114B of the devices, andthey are arranged so that the mutual plate surfaces may be in paralleland parts of the plate faces may overlap with each other in the incidentdirection of the light L.

The light shutter 110 shields the light L in the illustrated state, butby applying voltage of the same phase to piezoelectric elements 112A,112B formed on the driving portions of the devices, the shielding plate113A displaces to the left side of the figure and the shielding plate113B displaces to the right side of the figure, and therefore, theoverlapping condition of the shielding plates 113A, 113B changes, sothat ON/OFF control of light and light volume control can be performed.

Furthermore, a light shutter 120 shown in FIG. 21 (a) is made of twounits 121, 122 equipped with devices and shielding plates of the presentinvention, and two shielding plates 123A, 123B are respectively attachedto movable portions 124A, 124B of the devices, and they are arranged sothat the mutual plate surfaces may be in parallel and the plate facesmay entirely overlap with each other in the incident direction of thelight L. Then, in the shielding plates 123A, 123B, slits 125A, 125B areformed at the facing positions, respectively.

The light shutter 120 passes the light L through the slits 125A, 125B inthe state of FIGS. 21 (a), (b), but by applying voltage of the samephase to piezoelectric elements 122A, 122B formed on the drivingportions of the devices, the shielding plate 123A displaces to the leftside of the figure and the shielding plate 123B displaces to the rightside of the figure, and therefore, the overlapping condition of theslits 125A, 125B changes, so that ON/OFF control of light and lightvolume control can be performed. In the FIG. 21 (c), a state where apart of the light penetrates is shown, but it is also possible tocompletely shield the light L by changing the shapes and formingpositions of the slits 123A, 123B.

In contrast with this, it is also possible that to constitute a lightshutter so that the slits 125A, 125B may not overlap with each other andthe light L may be shielded in the state of FIGS. 21 (a), (b), and sothat the slits 125A, 125B may overlap with each other by the displacingof the shielding plates 123A, 123B and the light L may be passed.

In examples of FIGS. 20 (a), (b) and FIGS. 21 (a), (b), (c), the examplewhere two shielding plates are attached to the devices respectively, butin a light shutter of the present invention, it is also possible tocontrol the penetration and shielding of the light in such a way inwhich at least a shielding plate on one side is attached to the deviceand the shielding plate on one side is merely displaced. However, a wayof attaching both shielding plates to the devices is preferable in thatthe relative travel of the shielding plates can be increased.

Furthermore, in examples of FIGS. 20 (a), (b) and FIGS. 21 (a), (b),(c), the light shutter is constituted by two units, but it may beconstituted with three or more units. In this case, it can also be usedas a light aperture of changing the degree of opening of the overlappingparts or the like by variously setting the displacing directions of aplurality of shielding plates.

In a light shutter of the present invention, since a shielding plate isattached to a movable portion of the device of the present invention,the operation in the flapping direction of the shielding plate isrestrained. That is, since the shielding plate displaces while facing inthe incident direction of the light at all times, it can preferably beused since the ON/OFF control of light and light volume control can moreaccurately be performed.

As described above, a piezoelectric/electrostrictive device of thepresent invention can largely displace a movable portion, and it is noteasily affected by a harmful vibration in operation, and it is excellentin mechanical strength, handling efficiency, impact resistance, andmoisture resistance.

Furthermore, there is an advantage that it can be produced at a low costwhile raising reliability by having an integrated structure, by using asimple manufacturing method such as the green sheet laminating method.

Accordingly, it can be used as a sensor element for various kinds ofsensors such as an ultrasonic sensor or an acceleration sensor, anangular speed sensor, an impact sensor, or a mass sensor, besides anactive element such as various kinds of transducers, various kinds ofactuators, frequency-region functional parts (filter), transformers,oscillators or resonators for communication or motive power, vibrators,or discriminators, and especially, it is preferably used for variouskinds of actuators used in a mechanism of the displacement, positioningadjustment, or the angular adjustment of various kinds of precisionparts or the like of optical machinery and tools, precision machineryand tools or the like.

What is claimed is:
 1. A piezoelectric/electrostrictive devicecomprising: a driving portion which is driven by displacement of apiezoelectric/electrostrictive element; a movable portion which operateson the basis of a drive of the driving portion; and a fixed portion forsupporting said driving portion and said movable portion, wherein thedriving portion includes thin plates having major surfaces facing eachother and a thin film piezoelectric/electrostrictive element formed on asurface of at least one of the thin plates, and said fixed portion andsaid movable portion are connected by the driving portion.
 2. Thepiezoelectric/electrostrictive device according to claim 1, wherein themovable portion and the fixed portion are shaped like a rectangularparallelepiped, and the thin plates facing each other are spanned sothat sides of said movable portion and said fixed portion arecontinuous.
 3. The piezoelectric/electrostrictive device according toclaim 1, wherein the driving portion is driven in a directionperpendicular to the direction of displacement of thepiezoelectric/electrostrictive element.
 4. Thepiezoelectric/electrostrictive device according to claim 3, wherein themovable portion operates in a plane including the driving direction ofthe driving portion.
 5. The piezoelectric/electrostrictive deviceaccording to claim 1, wherein a piezoelectric/electrostrictive elementis formed on each thin plate, and one of thepiezoelectric/electrostrictive elements drives the driving portion whilethe other piezoelectric/electrostrictive element is used for detectionof displacement of the movable portion.
 6. Thepiezoelectric/electrostrictive device according to claim 1, wherein thedevice has at least two driving portions.
 7. Thepiezoelectric/electrostrictive device according to claim 1, wherein thewidth of each thin plate is 5 or more times the thickness of the thinplate.
 8. The piezoelectric/electrostrictive device according to claim1, wherein the piezoelectric/electrostrictive element is a layered typepiezoelectric/electrostrictive element in which a lower electrode, apiezoelectric/electrostrictive film, and an upper electrode arelaminated.
 9. The piezoelectric/electrostrictive device according toclaim 1, wherein the piezoelectric/electrostrictive element includes apiezo-electric/electrostrictive film, and first and second electrodeshaving a comb-like structure, and which has a structure where the firstelectrode and second electrode are mutually engaged with a gap portionof a constant width between mutual comb tooth portions.
 10. Thepiezoelectric/electrostrictive device according to claim 1, wherein themovable portion, the thinplates, and the fixed portion are made of anintegrally formed ceramic.
 11. The piezoelectric/electrostrictive deviceaccording to claim 10, wherein the movable portion, the thin plates, andthe fixed portion are made of completely stabilized zirconia orpartially stabilized zirconia.
 12. The piezoelectric/electrostrictivedevice according to claim 10, wherein at least the movable portion, thethin plates, and the fixed portion are constituted by green sheetlayered bodies.
 13. The piezoelectric/electrostrictive device accordingto claim 1, wherein a piezoelectric/electrostrictive film constitutingthe piezoelectric/electrostrictive element is made of a materialcontaining lead zirconate, lead titanate, and lead magnesium niobate asmain components.
 14. The piezoelectric/electrostrictive device accordingto claim 1, wherein a piezoelectric/electrostrictive film constitutingthe piezoelectric/electrostrictive element includes a materialcontaining bismuth sodium titanate as a main component.
 15. A lightshutter for controlling penetration and shielding of light by relativelydisplacing two shielding plates, comprising: apiezoelectric/electrostrictive device which comprises: a driving portiondriven by displacement of a piezoelectric/electrostrictive element; amovable portion operating on the basis of a drive of the drivingportion; a fixed portion for supporting said driving portion and saidmovable portion, wherein the driving portion includes thin plates havingmajor surfaces facing each other and a thin filmpiezoelectric/electrostrictive element formed on a surface of at leastone of the thin plates, and said fixed portion and said movable portionare connected by the driving portion; and at least one shielding plateattached to the movable portion of the piezoelectric/electrostrictivedevice.